There are devices known in the related art that prompt an operator driving a vehicle to operate the vehicle in a manner that improves fuel efficiency (see, for instance, patent literature 1). The device disclosed in patent literature 1 compares the actual fuel consumption with a specific target value and issues an alarm if the real fuel consumption is judged to be greater than the target value. The real fuel consumption is calculated by dividing the fuel consumption quantity by the traveling distance over which the vehicle has traveled.